It's really very simple, but there are a few basic principles you should understand before you get started. To use BTC you need software or hardware that manages wallets. A wallet is simply a "numbered account" in the public ledger. Anyone can easily instantly create as many wallets as they would like for privacy or security reasons. To spend the balance of a given wallet from anywhere in the world at any time all that is required is the key, so it is extremely important that you protect the keys to your wallets.

Just like with physical cash, it is not a good idea to walk around carrying large amounts of it (in case of theft or you somehow lose your wallet), but it is convenient to carry some spending cash. There are 2 basic categories of BTC wallets, hot (online) and cold (offline). For security reasons you should always keep larger amounts of BTC in a cold wallet. There are several methods of cold storage, but the most convenient for most people is probably a paper wallet. A popular hot wallet (for daily spending cash) that works with both iOS and Android mobile platforms is called My Wallet from blockchain.info. Below is a quick introduction video to help you get started.